Mixing 2 Different Octanes

[Gypo Logger]

Suppose I mix one gallon of 87 octane pump gas, and one gallon of 92 octane pump gas. Fish has told me, that instead of two gallons of 89.5 octane gas I have something closer to 92 (like between 90 and 91)? Is this true, and how so?
John

 

[John Lambert]

The mixed gas' octane rating will in general not be a linear function of the original constituents' octane ratings. Neither will it be a simple function in most cases. Rather, the octane rating becomes a quite complicated, non-linear function of some very small amounts of free radicals, such as hydroxyl and hydroxen peroxide, in the fuel. Essentially, there is no simple analytic way to predict the final octane rating of a fuel; rather, extensive tests with a calibrated engine are necessary.
Hope this helps John,
John

 

[Gypo Logger]

Sorry, I forgot the chainsaw related picture.
John

 

[Tony Snyder]

What octane would result from Millers Lite mixed 4 to 1 with Befeaters, then chased with Vodka and Seven Up?

How would a Stihl 026 run on that? If thats not cool for an 026s, maybe thats why I don't think they are the Welterweight Champions of the World.

 

[Gypo Logger]

Hi Tony, only Fish would know for sure, however I know about nitrous oxide, so I will try to put into words what I know about it.
You can improve maximum power stroke efficiency and minimize exhaust pumping losses by running the engine at lower RPM and/or improving the exhaust valve size, lift and port design. A big nitrous motor likes everything about the exhaust to be big. If it flows good enough the cylinder will blow down by bottom dead center, even at high RPM with relatively mild exhaust valve timing. There are many variables in the design and development of an all out nitrous engine. A mistake will cause the melt down of any brand of piston. The high strength of the KB piston will withstand detonation and severe abuse. Unfortunately, all pistons will melt and when cylinder pressure limits are exceeded, run away detonation can occur. The excess detonation heat makes the plugs, valves and piston so hot the ignition system alone can not be used to shut the engine down. Continued operation worsens the situation to the point of a total melt down. Designing a maximum performance nitrous engine is more of an exercise in heat management than it is in engine building.
Hope this helps.
John

 

[Weatherby]

Ok, I know absolutely nothing about this but doesn't fuel get separated into different grades by suspension. With one grade being less dense than the other, kind of like water float on top of oil. So when you mixed two different ratings together would there be enough of a specific gravity different for the two not to mix. I always wondered about this in cars. How would mixing oil in the gas affect the spearation? Forgive my stupidity.

Rob

 

[Bill G]

Weatherby,

Gypo/John meant this as a joke.


John,

No offense intended but do you ever get any logging done ? It seems like you spend a heck of a lot of time taking great pictures and posting responses You must be able to type 100 words per minute.

Bill

 

[Gypo Logger]

Bill, you shoudn't blow my cover like that. I think weatherby was just trying to get me to give more of my convuluted responses.
And just to think that this thread could have reached 500, oh well.
I did the math, and for every reply I make here, I cut down approx. 1/6 of a tree. So, when I get an abor brain fart, I just pack things up, come home and post @ 3 words/minute. In other words I cut only 300 trees/annum.
Weatherby, I heard thru the grapevine that you need an 088, my email has been frapulated as of late so please feel free to call me at: Franks Planks, 905 702 8357.
Thanks,
John

 

[sedanman]

Just a theory here folks, I think when John was doing to the 015L oxygen consumption test in the fridge..........he was in there with a stopwatch!

 

[Chainsaw_Maniac]

This may be a joke to Gypo, but I've actually done exactly that, mixed fuel of differant octane. I don't really care about any math though, all I know is it worked. lol.

 

[Rootbeer]

John start by inserting your data here.http://www.engr.colostate.edu/~allan/thermo/page8/HTCoefficient/htcoefficient.html

Then afterwards the data will show how this gas mixture works. I have spent countless hours trying to find the right mix for my mini bikes. I presume that you have done your math first only to find there is greater gains in using BPVP69-71 115 oct.

 

[Jumper]

Gas

SUNOCO mixes gas all the time-in reality there is only two or three tanks containing Reular no-lead and , High Test 92 and Ultra 94 no lead high test, and all the grades in between are mixtures of two grades thus they are ble to offer six or so grades of gas.

 

[bwalker]

Jumper is right. There are two grades of gas. 89 is amixture of 87 and 92.

 

[Bill G]

Come on guys,

There are only two grades of gas, 10% ethanol and non ethanol. In a few stations you can buy 80% ethanol. The rest of the time you are buying the same gas at a higher price. It is just another way to get a few dimes more. Now if you really want a high octane fuel go with a Cam 2 or Turbo Blue they are definately different.

Bill

 

[Harley]

Bill G,

Here, we can only get stuff with ethanol mixed in it. Too many emissions problems in the suburbs of Philadelphia.

 

[Chainsaw_Maniac]

Originally posted by Harley
Bill G,

Here, we can only get stuff with ethanol mixed in it. Too many emissions problems in the suburbs of Philadelphia.

I never use gas with ethonol in it in my chainsaws. The older Stihl owners manuals say that it contains fuel addatives that can damage the engine.

 

[bwalker]

Ethanol as a fuel additive stinks big time. In my area Sunoco is the only one who sells it. In MI its a state law that people selling ethanol laced fuel must print as doing so on the pump.

 

[Bill G]

bwalker,

As far as I know all states require proper labeling of fuels as to additives and octane level. I would imagine all states also get quite strict on off-road diesel. The DOT here will set up road blocks and dip tanks of any diesel enigine on the road. I have heard rumors of the fine being $10,000. Still when it is running about $0.50 per gallon cheaper guys will chance it.

I would agree with not using an ethanol blended fuel in older chainsaws but it will not cause problems in any vehicle. We have been burning it for over 20 years in engines that are more than 50 years old. In the past 20 years we have never had one of those engines apart.

Bill

 

[bwalker]

older chainsaws but it will not cause problems in any vehicle.

I wouldnt be so fast to say that. My ms 260 came from the factory very lean. Had I thrown 10% fuel into the mix it would have seized. Not to mention the fact that ethanol fuels store poorly, attract water from the atmosphere, give less fuel economy, and do not cut pollution beyond what you could do by simply setting your carb right. BTW etahnol actually gives off formaldehyde as one of its combustion by products. If it where not for the corn lobby the stuuf would not even be considered for a fuel additive. MTBE works much better, but I would still rather have non oxy gas.

 

[Fish]

So Lambert,
I see the fishing is good up your way!